Gas turbine engine with selective flow path

ABSTRACT

A method of operating a gas turbine engine includes generating a flow of combustion products from a gas turbine generator that has a gas generator axis of rotation. A duct is oriented in a first position to direct the flow of combustion products that have passed over at least one gas generator turbine rotor through a fan drive turbine in response to a first desired flight condition. An axis of rotation of the fan drive turbine is transverse to a gas generator axis of rotation. The duct is oriented in a second position to direct the flow of combustion products that have passed over at least one gas generator turbine rotor through an augmentor section in response to a second desired flight condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 14/713,187filed May 15, 2015, which claims priority to U.S. Provisional PatentApplication No. 62/001,882, filed on May 22, 2014.

BACKGROUND OF THE INVENTION

Gas turbine engines are known and typically include a fan delivering airas bypass air into a bypass housing and further delivering air into acore engine. Air in the core engine is directed into a compressor whereit is compressed. The compressed air is then delivered into a combustionsection where it is mixed with fuel and ignited. Products of thiscombustion pass downstream over turbine rotors, driving them to rotate.

Recently, it has been proposed to increase the diameter of the fan to,in turn, increase bypass ratios, or the volume of air delivered asbypass or propulsion air compared to the volume of air delivered intothe core engine. However, the ability to make this increase is somewhatlimited by the packaging envelope available on an aircraft.

It has been proposed to replace a single large diameter with a pluralityof fan rotors. However, the proposals for driving the plurality of fanrotors have deficiencies in general.

SUMMARY OF THE INVENTION

In one exemplary embodiment, a method of operating a gas turbine engineincludes generating a flow of combustion products from a gas turbinegenerator that has a gas generator axis of rotation. A duct is orientedin a first position to direct the flow of combustion products that havepassed over at least one gas generator turbine rotor through a fan driveturbine in response to a first desired flight condition. An axis ofrotation of the fan drive turbine is transverse to a gas generator axisof rotation. The duct is oriented in a second position to direct theflow of combustion products that have passed over at least one gasgenerator turbine rotor through an augmentor section in response to asecond desired flight condition.

In a further embodiment of the above, the gas generator includes atleast one compressor rotor, at least one gas generator turbine rotor anda combustion section.

In a further embodiment of any of the above, the first desired flightcondition is subsonic flight.

In a further embodiment of any of the above, the second desired flightcondition is supersonic flight.

In a further embodiment of any of the above, the flow of combustionproducts passes over at least one gas generator turbine rotor prior toentering the duct.

In a further embodiment of any of the above, the fan drive turbinedrives a shaft and the shaft engages gears to drive at least two fanrotors.

In a further embodiment of any of the above, at least two fan rotorsinclude a variable inlet and a variable outlet. The variable inlet andthe variable outlet are in an open position when the duct is in thefirst position and in a closed position when the duct is in said secondposition.

In a further embodiment of any of the above, the augmentor sectionincludes a variable exhaust. The variable exhaust is in a closedposition when the duct is in the first position and in an open positionwhen the duct is in the second position.

In a further embodiment of any of the above, an axis of rotation of thegas generator is generally perpendicular to an axis of rotation of theshaft.

In a further embodiment of any of the above, an axis of rotation of thegas generator is generally coaxial with an axis of rotation of at leasttwo fan rotors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a gas turbine engine.

FIG. 2 is a front view of the FIG. 1 engine.

FIG. 3 shows a first embodiment in a first configuration.

FIG. 4 shows the first embodiment in a second configuration.

FIG. 5 shows a dual configuration of FIG. 3.

FIG. 6 shows a dual configuration of FIG. 4.

DETAILED DESCRIPTION

A gas turbine engine 20 is illustrated in FIG. 1 having a gas generator22. The gas generator 22 may be a two spool gas generator having a lowspeed spool in which a first upstream compressor rotor 24 driven by adownstream or low pressure turbine rotor 26. A high speed spool includesa high pressure compressor rotor 28 rotating with a high pressure orupstream turbine rotor 30. A combustion section 32 is positionedintermediate rotors 28 and 30.

An exhaust duct 34 is positioned downstream of the gas generator 22 andreceives products of combustion which have driven the turbine rotor 26to rotate. These products of combustion pass across a fan drive turbine36 mounted in a housing 37. The fan drive turbine 36 drives a singleshaft 38 that engages a plurality of bevel gears 40 to, in turn, driveshafts 41 associated with fan rotors 42, 44, 46 and 48. Each of the fanrotors 42, 44, 46 and 48 are mounted within separate housings 50.

By providing the single shaft 38, which drives at least four fan rotorsand by utilizing a fan drive turbine 36 which is positioned downstreamof the last turbine rotor 26 in the gas generator 22, this disclosureprovides compact packaging, while still providing adequate drive for thefan rotors 42, 44, 46 and 48.

FIG. 2 is a front view of an aircraft wing 80, which may mount an enginesuch as engine 20. As shown, the gas generator is associated with thehousing 37. The fan rotors 42, 44, 46 and 48 have diameters that are notunduly large, such that they fit within the packaging window ofassociated wing 80.

The basic engine as described above is disclosed in co-pending U.S.patent application Ser. No. 61/989,675, entitled “Gas Turbine EngineWith Distributed Fans,” filed on May 7, 2014. This basic fan structurecan be incorporated into a gas turbine engine arrangement having one ormore gas generators, and paired sets of the distributed fan.

As shown in FIGS. 3 and 4, a fan set 130 includes an engine 100 having agas generator 102 for driving a fan drive turbine 104 or an augmentor106. Products of combustion from the gas generator 102 are directed tothe fan drive turbine 104 or the augmentor 106 by a moveable duct 108.An exhaust path when the moveable duct 108 is directed to the fan driveturbine 104 is generally perpendicular to an exhaust path when themoveable duct 108 is directed to the augmentor 106. In this embodiment,the moveable duct 108 is a three bearing swivel duct. However, otherducts capable of directing the products of combustion from the gasgenerator 102 to the fan drive turbine 104 and the augmentor 106 couldbe used.

When the gas generator 102 is used to drive the fan drive turbine 104 asshown in FIG. 3, products of combustion from the gas generator 102 passinto an exhaust duct 110. A shaft 112 rotates about an axis Y, while thegas generator 102 rotates about an axis X. The axis X is generallyperpendicular to the axis Y. Shafts 114 are driven by shaft 112 to turnfan rotors 116 and 118. The shafts 114 extend in a direction generallyparallel to the axis X and perpendicular to the axis Y. Although theshaft 112 is shown turning two separate rotors 116 and 118, additionalrotors could be turned by the shaft 112.

A variable inlet 120 surrounds an inlet to the rotors 116 and 118 and avariable outlet 122 surrounds an outlet of the rotors 116 and 118 andthe exhaust duct 110. When the moveable duct 108 engages the driveturbine 104 to turn the rotors 116 and 118, the variable inlet 120 andthe variable outlet 122 are in an open position and an augmentor outlet128 is in a closed position to reduce drag.

When the gas generator 102 is used to drive the augmentor 106, theaugmentor outlet 128 is opened and products of combustion from the gasgenerator 102 pass into an augmentor duct 126. The variable inlet 120and the variable outlet 122 close to reduce drag.

Fuel spray rails 124 extend into the flow path formed by the augmentorduct 126 to inject fuel which is ignited by an igniter 125 to produce anafterburner effect from the augmentor 106.

FIG. 5 shows an arrangement using the two fan sets 130 with the moveableduct oriented to drive the fan drive turbine 104. Utilizing the two fansets 130 in this orientation creates a higher propulsive efficiency withlower fuel consumption and exhaust temperatures for long range cruisesituations.

FIG. 6 shows an arrangement using the two fan sets 130 with the moveableducts 108 oriented to engage the augmentors 106. Utilizing the two fansets 130 in this orientation allows for supersonic or elevated speeds oftravel with a higher fuel consumption than the arrangement shown in FIG.5.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this disclosure. The scope of legal protection given tothis disclosure can only be determined by studying the following claims.

1. A method of operating a gas turbine engine comprising: generating aflow of combustion products from a gas turbine generator having a gasgenerator axis of rotation; orienting a duct in a first position todirect said flow of combustion products having passed over at least onegas generator turbine rotor through a fan drive turbine in response to afirst desired flight condition, wherein an axis of rotation of said fandrive turbine is transverse to a gas generator axis of rotation; andorienting said duct in a second position to direct said flow ofcombustion products having passed over said at least one gas generatorturbine rotor through an augmentor section in response to a seconddesired flight condition.
 2. The method of claim 1, wherein said gasgenerator includes at least one compressor rotor, at least one gasgenerator turbine rotor and a combustion section.
 3. The method of claim1, wherein said first desired flight condition is subsonic flight. 4.The method of claim 3, wherein said second desired flight condition issupersonic flight.
 5. The method claim 1, wherein said flow ofcombustion products pass over said at least one gas generator turbinerotor prior to entering said duct.
 6. The method of claim 1, whereinsaid fan drive turbine drives a shaft and said shaft engaging gears todrive at least two fan rotors.
 7. The method of claim 6, wherein said atleast two fan rotors include a variable inlet and a variable outlet,said variable inlet and said variable outlet are in an open positionwhen said duct is in said first position and in a closed position whensaid duct is in said second position.
 8. The method of claim 7, whereinsaid augmentor section includes a variable exhaust, said variableexhaust is in a closed position when said duct is in said first positionand in an open position when said duct is in said second position. 9.The method of claim 6, wherein an axis of rotation of said gas generatoris generally perpendicular to an axis of rotation of said shaft.
 10. Themethod of claim 6, wherein an axis of rotation of said gas generator isgenerally coaxial with an axis of rotation of said at least two fanrotors.